Alt Text Character Limit: 100, 125 or 150?

Sample file

A general CSV export, including an alt_length column you can sort by.

file,alt_text,alt_length,description,hashtags,platform,language
logo.png,Neartool logo,13,A simple wordmark.,,general,en
bridge.jpg,"Red suspension bridge crossing a wide river at sunrise, with mist along the water",81,A red suspension bridge at sunrise.,,general,en
kitchen.jpg,"Bright kitchen with white cabinets, a wooden island with three stools, hanging pendant lights and a window above the sink",121,A bright modern kitchen.,,general,en

Steps

1. Decide which limit your team or platform recommends: 100, 125 or 150 characters.
2. Paste your alt text into the alt text checker, one line per image, and choose the same limit.
3. Shorten flagged lines by removing words such as image of and by cutting repeated detail.
4. Put the most important detail in the first words, in case the text is cut or skimmed.
5. For images that need more explanation, add a caption or a text description on the page.

Start with the Alt text checker, then check the text with the alt text checker.

What the guidance actually says

Neither WebAIM nor the W3C accessibility tutorials set a character limit for alt text. They ask for text that conveys the purpose of the image, briefly. The popular figure of 125 characters comes from older screen reader behaviour and from SEO and accessibility tools that adopted it as a rule of thumb. Some platforms repeat it, such as Shopify, which recommends 125 or fewer while accepting up to 512.

So treat the numbers as house style rather than law. What matters is that every image gets text that is as long as it needs to be and no longer.

A practical approach is to measure first. Run your existing alt text through a checker, sort by length, and look at the longest lines. Most of the time the long ones hold two ideas, and splitting them into a short alt attribute plus a caption or a sentence of page text reads better for everyone, including people who use a screen reader.

Choosing between 100, 125 and 150

100 characters suits product grids, icons and simple photos, where one short phrase does the job. 125 characters is the common middle ground and the safest default if you have no other rule. 150 characters gives room for photos with context, such as news or editorial images, where the subject, setting and action all matter.

Whichever you choose, apply it consistently so reviewers have one number to check against.

Match the limit to the image

A decorative image needs no alt text at all, so use an empty alt attribute. A logo needs only the organisation's name. A chart needs the main takeaway in alt text and the data in a table or paragraph near it. A person in a photo needs only what is relevant to the page. Length should follow the image's job, not a quota.

Auditing a batch

Export your alt text to CSV and the file includes an alt_length column. Sort it from longest to shortest to find the lines to trim first. The same lines can be pasted into the checker, which also catches file names, duplicates and keyword lists.

Limits and facts

Frequently asked questions